Bis(sulfonylimide)ruthenium(VI) Porphyrins: X‐ray Crystal Structure and Mechanism of CH Bond Amination by Density Functional Theory Calculations

Abstract The X‐ray crystal structure of [Ru VI (NMs) 2 (tmp)] (Ms=SO 2 ‐ p ‐MeOC 6 H 4 ; tmp=5,10,15,20‐tetramesitylporphyrinato(2−)), a metal sulfonylimide complex that can undergo alkene aziridination and CH bond amination reactions, shows a RuN distance of 1.79(3) Å and Ru‐N‐S angle of 162.5(3)°. Density functional theory (DFT) calculations on the electronic structures of [Ru VI (NMs) 2 (tmp)] and model complex [Ru VI (NMs) 2 (por 0 )] (por 0 =unsubstituted porphyrinato(2−)) using the M06L functional gave results in agreement with experimental observations. For the amination of ethylbenzene by the singlet ground state of [Ru VI (NMs) 2 (por 0 )], DFT calculations using the M06L functional revealed an effectively concerted pathway involving rate‐limiting hydrogen atom abstraction without a distinct radical rebound step. The substituent effect on the amination reactivity of ethylbenzene by [Ru VI (NX) 2 (por 0 )] (X=SO 2 ‐ p ‐YC 6 H 4 with Y=MeO, Me, H, Cl, NO 2 ) was examined. Electron‐withdrawing Y groups lower the energy of the LUMOs of [Ru VI (NX) 2 (por 0 )], thus facilitating their interaction with the low‐lying HOMO of the ethylbenzene CH bond and hence increasing the reactivity of [Ru VI (NX) 2 (por 0 )]. DFT calculations on the amination/aziridination reactions of [Ru VI (NSO 2 C 6 H 5 ) 2 (por 0 )] with pent‐4‐enal, an aldehyde substrate bearing acyl, homoallylic, and allylic CH bonds and a CC bond, revealed a lower reaction barrier for the amination of the acyl CH bond than for both the amination of the other CH bonds and aziridination of the CC bond in this substrate.